The present invention relates to a solid state imaging apparatus in which a plurality of photoelectric conversion sections are arranged in an array, a method for driving the solid state imaging apparatus and a camera using the solid state imaging apparatus.
FIG. 10 is a diagram illustrating a general circuit configuration for a MOS type image sensor, i.e., a known solid imaging apparatus (e.g., see M. H. White, D. R. Lange, F. C. Blaha and I. A. Mach, “Characterization of Surface Channel CCD Image Arrays at Low Light Levels”, IEEE J. Solid-State Circuits, SC-9, pp. 1-13 (1974)).
As shown in FIG. 10, a photoelectric conversion cell includes a photodiode (PD) section 101, a transfer transistor 113, a reset transistor 122, a pixel amplifier transistor 123, a select transistor 152, a floating diffusion (FD) section 109, a power supply line 131 and an output signal line 138.
The PD section 101 of which the anode is grounded is connected to the drain of the transfer transistor 113 at the cathode. The source of the transfer transistor 113 is connected to the respective sources of the FD section 109, the gate of the pixel amplifier transistor 123 and the source of the reset transistor 122. The gate of the transfer transistor 113 is connected to a read-out line 134. The reset transistor 122 which receives a reset signal 137 at the gate includes a drain connected to the drain of the pixel amplifier transistor 123 and the power supply line 131. The source of the pixel amplifier transistor 123 is connected to the drain of the select transistor 152. The select transistor 152 receives a selection signal SEL at the gate and includes a source connected to the output signal line 138.
The output signal line 138 is connected to the source of a load gate 125. The gate of the load gate 125 is connected to a load gate line 140 thereof and the drain is connected to a source power supply line 141.
In this configuration, a predetermined voltage is applied to the load gate line 140 so that the load gate 125 becomes a constant current source, and then the transfer transistor 113 is temporarily turned ON to transfer charge photoelectric-converted in the PD section 101 to the FD section 109. Then, the potential of the PD section 101 is detected by the pixel amplifier transistor 123. In this case, by turning the select transistor 152 ON, signal charge can be detected through the output signal line 138.
However, in the known solid state apparatus, four transistors 113, 122, 123 and 152 and five lines 131, 134, 137, 138 and 150 are required for total in each photoelectric conversion cell. Accordingly, the areas of transistor and line sections in a cell are increased. For example, if a photoelectric conversion cell is designed, assuming that the area of a photoelectric conversion cell is 4.1 μm×4.1 μm, with the design rule of 0.35 μm, the aperture ratio of the PD section 101 to the photoelectric conversion cell is only about 5%. Therefore, it is difficult to ensure a sufficiently large area of opening of the PD section 101 and also to reduce the size of the photoelectric conversion cell.